Urinary Excretion and Plasma Levels of Free Ninhydrin Reactive Compounds in X-Irradiated Rats

¹ From the Biological and Medical Sciences Division, U. S. Naval Radiological Defense Laboratory, San Franciso, California

Urinary excretion and plasma levels of ninhydrin-reactive compounds in x-irradiated rats were quantitatively studied. In the urinary excretion studies fasted rats were exposed to either a sublethal (450 r) or superlethal (2500 r) dose of whole-body 250 kvp x-rays. Twenty-four-hour urines, taken from two days preirradiation to 3 days postirradiation, were analyzed for ninhydrin-reactive compounds. During the day following x-irradiation, rats exposed to either sublethal or superlethal irradiation excreted increased amounts of urinary taurine, cysteic acid, leucine and valine. In the plasma studies four groups of rats were exposed to 600 r of whole-body x-irradiation. At 6, 12, 24 and 30 hours after irradiation plasma was analyzed for ninhydrin-reactive compounds and creatinine. Transitory elevations in plasma concentrations of lysine, glutamine, taurine, methionine, valine and leucine were observed, while elevations in the levels of arginine, serine plus glycine, threonine, alanine and creatinine were not noted. The increased urinary excretion of nonglycogenic amino acids and the increased plasma concentrations of the nonglycogenic amino acids may be the result of a breakdown of protein or protein-like compounds to amino acids with the subsequent rapid conversion of the excess glycogenic amino acids to liver glycogen. The early excessive excretion of taurine in the x-irradiated rat suggests an increased oxidation of sulfur containing compounds.